1. Technical Field
The present invention relates in general to a new and improved imaging system and method for producing an enhanced image. The invention more particularly relates to the projection of a full color image with enhanced brightness and contrast.
2. Background Art
Full color imaging systems, such as projection television systems, have in the past, employed three separate cathode ray tubes for each one of the red, green and blue light components. A large lens was employed for combining the various color components for projecting the full color image.
A more compact and less expensive imaging system was disclosed in Japanese patent 2,505,758. The patented system included a polarizing beam splitter and a prism optical arrangement to split the incident white light into three separate color components. Three separate liquid crystal display panels for each color modulated the individual light components. The three modulated light components were then reflected back to the beam splitter to, in turn, project the resulting full color combined image.
Such a polarizing system employs fewer components, and thus is less expensive to manufacture. When it is desirable to locate the projection system at various different distances from the viewing surface, such a system was also more readily focused onto a remote viewing surface, such as a screen.
However, the principal drawback of the patented system is that the brightness and contrast were not entirely satisfactorily. In this regard, if the brightness were increased, the contrast would degrade and could become less than acceptable for some applications.
The critical contrast characteristics in the patented system relate to the ratio of the reflected S component to the reflected P component of the light incident on the polarizing beam splitter surface. To increase the brightness, the reflected S component is increased, but the reflected P component would also increase. Thus, in order to have acceptable contrast, the brightness is reduced to an unacceptable level for many applications.
In the case of the patented system, the brightness is unacceptably low to achieve minimal acceptable contrast. In this regard, the throughput or Etendue is, by definition, equal to the solid angle times the light emitting aperture area. The size of the solid angle helps determine the amount of the brightness. However, by increasing the solid angle of the incident light to increase the brightness, the contrast becomes degraded. Thus, in a practical application of the patented system, the overall throughput would be greatly attenuated to achieve minimally acceptable contrast, and thus the brightness of the resulting image is degraded and can be less than acceptable for many applications.
Therefore, it would be highly desirable to have a new and improved compact imaging system, which achieves an enhanced brightness, as well as an enhanced contrast of the full color image.